(1) Bridge closure and hole closure
Most kinds of pear trees are tall trees. In the absence of ideal pear dwarfing rootstocks, pear trees cultivated in China are basically arbor rootstocks. Before the crown control measures were solved, the cultivation mode of large crown and sparse planting has been adopted for thousands of years.
Too high and too large a crown has many disadvantages: pruning, spraying chemicals, thinning flowers and fruits, picking fruits and other tree management is very inconvenient; It is labor-consuming, laborious and inefficient, and it is difficult to get high-yield and high-quality commercial fruits. The crown is high, the diameter is large, the ventilation and light transmission are poor, the invalid crown area in the crown is large, and only the top and peripheral surfaces of the tree bear fruit. Therefore, crown enlargement before fruit setting and crown control after fruit setting are one of the important characteristics of pear tree shaping and pruning. Especially for densely planted pear trees, crown control is particularly important. The higher the density, the earlier the crown control. If the control is not timely and appropriate, the whole garden will be closed, not only the yield and quality will drop sharply, but also the close planting will fail. Therefore, the crown shape should be selected according to the planting density. That is, the big crown shape for sparse tree planting (such as basic three-branch semicircle, cross, natural round head shape); Medium-dense crown shape (such as trifoliate shape, happy shape, improved fan shape); Small crown shapes (such as spindle shape, single-layer high-opening heart shape, cylinder shape and fan shape) are densely planted. It is also necessary to control the crown according to the allowable range of plant spacing. Generally, it is required that the height of the tree is less than the row spacing, and no rows are closed. A light rail with a width of1.5 ~ 2m should be provided, and there can be a 10% ~ 20% connection between trees. If it is too high, put it down; if it is too wide, take it back. Through telescopic pruning, the crown of the tree is controlled within its due range. Take early measures to promote flowering and early fruiting, and top with fruits.
(2) Strong polarity and opening angle
Most varieties of pear trees are very polar because of their small branching angle, upright growth and high position. This upright growth is a sign of vigorous vitality. This may be the reason why pear trees have long life, strong resistance and wide suitable planting area.
Polarity has both advantages and disadvantages in pruning. On the one hand, in the young tree stage, polarity can be used to promote the rapid growth of trees, and the crown can expand and form quickly. By increasing the angle of main branches, the crown can extend laterally, thus occupying more space and competing for more light energy, laying a good foundation for early maturity and high yield. For weak trees and weak branches, the angle can be raised and truncated at the branches and buds at the high point, so as to promote their regeneration and rejuvenation and prolong the fruit-bearing life. On the negative side, too strong polarity can easily lead to too great difference in growth potential between the central trunk and the main branch, and between the main branch and the lateral branches. It has some shortcomings, such as being strong and weak, strong and weak, strong and weak, strong and weak before and after. These disadvantages are only beneficial to the growth of trees, not to the results. To solve these problems, we should adopt the method of polarity conversion, such as changing angle, displacement, height, direction, dispersion and so on.
(1) To prevent and overcome the pruning method that the center is too thick and strong, and the upper part is strong and the lower part is weak, you can leave more main branches in the layer, support the lateral branches of the door and the space under the layer, make the central trunk rotate in multiple branches, and intercept water and nutrients. At the same time, the strong branches on the upper part of the central trunk are drained in time to inhibit the upper part and promote the lower part. Or bend the trunk in the center in the shape of a tree. When it is too high, it will bow its head happily and press its strength on the branches below.
(2) The main way to overcome the pruning method of strong main branches and weak main branches is to increase the angle of main branches, reduce the height of branches, and use weak branches, weak buds, outer branches and outer buds as the heads. Opening angle should start from the branch age of young tree 1 ~ 2 years, and change the angle by pulling, changing, separating, peeling, pressing and dropping branches. If the branches are old and hard, they must be supported by sticks. If conditions permit, you can change your head and use exogenous branches as your head.
(3) Low branching ability, selection and retention of main branches
Most pear varieties have weak branching formation, generally only 1 ~ 2 long branches are issued, and 3 branches are issued individually. For example, the branching ability of pear line Jing is11.9%; Pak Lei crisp pear is 9. 1%, Cili is 1 1%, and Zaosu pear is 9.6%. Shan Zhi in the middle and late period of pear is10.4%; In foreign pears, the percentage of 1 1.5%. In view of this feature, we should pay attention to: The ability to form branches is low, and the crown is sparse, so the main branches and side branches can be left appropriately. In order to grow more branches, wounds can be carved on the buds that need to grow branches in the central trunk during the plastic surgery period to promote germination; ? Pay attention to extend the third and fourth buds of branch cutting, stay on both sides, and carve buds at the same time to promote the development of lateral branches; ? Due to the low branching ability, the crown is loose and hollow after increasing the angle of main branches, so the principle of pear tree shaping is to cut lightly and leave more auxiliary branches and various branchlets. In the first four years, the branches were basically not sparse. In this way, it gradually gives way to the main branch, making it thinner or shrinking into large and small branches.
(4) Strong germination ability, long residence time and long release time.
Most pear varieties have high germination ability. For example, 100% after pruning in Jing Pak Lei and 95% after long branch cutting; Crispy pears are 75% and 84% respectively; 83% and 88% of Zaosu pear; Zaobali pear is 80% and 90%.
Pear trees have high germination ability, low branching ability and large proportion of short branches. A considerable number of short-branch flower buds can be formed in 3 ~ 4 years after planting, which is the basis of early fruit and early harvest of pear trees. Pruning should promote the proliferation of short branches and early fruiting.
The branches of pear trees have a very good response to long-term growth, especially when the branches with good fertilizer and water conditions or upright and strong are bent, pulled, dropped, peeled, pressed and turned back, and then sprayed with fertilizer on the leaves, it is easy to become flowers. Under the principle of light pruning and multi-branching, it is an important method to keep long branches, put them first and then shrink them, or put them first and then cut them. For example, the investigation on the slow-release effect of Zaosu pear showed that the total length of branches was 108 ~ 148 cm, and 25.9 sprouted, including 2 short branches and 2 flower buds 12.438+0, accounting for 46.7% of the sprouting number. After the two-year-old trees of Zaosu pear were bent and slowly released, the average yield of three-year-old trees was 5.2 ~ 6.2 kg.
Pear trees have low branching ability, often extending uniaxial, and the back part is the result of short fruit branches strung together. After bearing fruit for several years in a row, it is easy to cause premature aging, rapid outward migration and even sagging of the fruiting part. Therefore, when it is put into a certain length and years, it should be retracted and rejuvenated in time.
(5) Short fruiting and rejuvenation of branches.
80% ~ 90% of the fruits of adult pear trees are borne on short fruit branches and short fruit branches. How to carefully prune short branches and short fruit branches is one of the important characteristics of pear tree pruning.
Short fruit branches are a long series of short branch flower buds formed in the same year or the following year after the long branches are slowly released; Or after the flower buds at the top of the long and middle fruit branches bear fruit, the lower part forms short fruit branches. Truncation and pruning of these two kinds of branches with short flower buds, leaving only 2 ~ 3 flower buds behind, is a small short fruit branch group. The fruiting branches or buds on the short fruiting branches continue to blossom and bear fruit every 1 year, and form short fruiting branches after 3 ~ 5 years. For this kind of short fruit branch, it is necessary to remove too many flower buds, leave one before and after, and stay far away from each other, so as to stay young all the time, and to ensure that the old branches of the tree are not old and achieve high and stable yield.
(6) Longevity and rejuvenation of latent buds
The long life of latent buds is also a very favorable feature of pear trees. Even if the trees shrink again without branches for decades or even hundreds of years, with the management of underground fertilizer and water, they can still grow long branches. After 2 ~ 3 years of renewal, new crown results can be formed, which is conducive to the renewal and rejuvenation of weak branches and weak trees.